The role of triggering factors, such as mental stress and physical exercise, in causing cardiovascular events is being evaluated. We will evaluate effects of mental stress on ventricular tachycardia induction, cycle-length, and termination in patients with implantable defibrillators and inducible monomorphic VT which is pacer-terminable. Only a fraction (5) of planned enrollment (50) has been met and no statistical analysis has been performed. We plan to continue until planned enrollment is complete.